CN114915182A - An application circuit with ultra-wide output voltage and wide constant current range - Google Patents

Abstract

An ultra-wide output voltage and wide constant current range application circuit relates to the field of EDI pure water equipment or intelligent chargers. The problem of current EDI pure water equipment or intelligent charging ware can't realize stablizing the technique not enough of super wide output voltage scope, wide constant current scope power supply is solved, including: the device comprises an input circuit, an LDO power supply circuit, a power transmission output circuit, an input undervoltage protection detection circuit, a PWM (pulse-width modulation) drive control circuit, an overcurrent and overvoltage protection circuit, a voltage stabilization sampling feedback circuit, a constant current sampling feedback circuit and a constant current value regulating circuit; in the whole power end from light load to heavy load, the working frequency is not changed, and the intermittent and frequency reduction are not caused; the overcurrent protection mode is changed from the trigger mode to the limit mode, the output mode is changed from the reference voltage mode through the constant current value regulating circuit, constant currents of different gears are realized, the wide-range voltage stabilization and constant current functions are realized, and the overvoltage and short circuit protection device has the input undervoltage, input reverse connection, output overcurrent, overvoltage and short circuit protection functions.

Description

An application circuit with ultra-wide output voltage and wide constant current range

technical field

The invention relates to the field of EDI pure water equipment or intelligent chargers.

Background technique

In the field of EDI (Continuous Electric Desalination) pure water equipment or smart chargers, a very wide power output range is required, such as smart chargers, which need to adapt to different strings of batteries and batteries of different capacities, and sometimes require a charging range from 0-96VDC, The output constant current range is 0.5-3A. Another example is some EDI pure water equipment, which requires an output voltage of 2-110VDC and a constant current range of 50-200mA. This is extremely difficult to achieve for conventional power supplies. Conventional power supplies must be stable. The working range is generally only up to 30-110VDC, and a more suitable solution is needed to achieve stable ultra-wide output voltage range, wide constant current range power supply, and meet the reliable and stable working requirements of EDI equipment/chargers.

In the existing conventional solution, the PWM control chip will enter the intermittent and frequency reduction mode at light load, resulting in unstable operation at extremely light load, and it is difficult to take into account the stability of the extremely wide loop, and the loop is too slow. The overcurrent protection problem is triggered in the process of charging the output capacitor when it is just powered on. The output voltage is too high and the charging time is long. The large current generated at this time will cause the overcurrent protection of the PWM control chip.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the technical deficiencies that the existing EDI pure water equipment or intelligent charger cannot achieve stable ultra-wide output voltage range and wide constant current range power supply, and proposes an ultra-wide output voltage and wide constant current range application circuit .

In order to solve the technical problem proposed by the present invention, the technical scheme adopted is:

An ultra-wide output voltage and wide constant current range application circuit, characterized in that the circuit includes: an input circuit, an LDO power supply circuit, a power transmission output circuit, an output circuit, an input under-voltage protection detection circuit, a PWM drive control circuit, Overcurrent and overvoltage protection circuit, voltage regulation sampling feedback circuit, constant current sampling feedback circuit and constant current value adjustment circuit; among them,

Input circuit, used for DC power supply input, power supply for LDO power supply circuit and power transmission output circuit;

The LDO power supply circuit is used to convert the input voltage of the input circuit into the voltage required by the stable PWM drive control circuit to supply power to the PWM drive control circuit;

The power transmission output circuit is used to transform, rectify and filter the input voltage of the input circuit and output it through the output circuit;

The output circuit is used to supply power to the electrical equipment;

The input under-voltage protection detection circuit is used to detect the input voltage of the input circuit, and provide the input under-voltage protection signal for the PWM drive control circuit when the input voltage is lower than the preset value;

The overcurrent and overvoltage protection circuit is used to detect the output voltage of the power transmission output circuit and the primary current of the transformer of the power transmission output circuit. Provide overvoltage or overcurrent protection signal for PWM drive control circuit when setting value;

The voltage regulator sampling feedback circuit is used to detect the output voltage of the power transmission output circuit, and compare it with the reference voltage provided by the constant current value adjustment circuit to provide the PWM duty cycle adjustment feedback signal for the PWM drive control circuit;

The constant current sampling feedback circuit is used to detect the output current of the power transmission output circuit and feed it back to the PWM drive control circuit;

The constant current value adjustment circuit is used to adjust the constant current sampling reference value of the constant current sampling feedback circuit;

The PWM drive control circuit is used to adjust the PWM duty cycle according to the feedback signals of the voltage regulation sampling feedback circuit and the constant current sampling feedback circuit, drive the power transmission output circuit, and perform undervoltage protection according to the input undervoltage protection signal of the input undervoltage protection detection circuit. Overvoltage protection, overcurrent protection is performed according to the overvoltage or overcurrent protection signal provided by the overcurrent and overvoltage protection circuit.

The technical solutions that further limit the invention include:

The LDO power supply circuit includes a first resistor, a second resistor, a second transistor, a second diode, a first Zener diode and a first capacitor; one end of the first resistor is connected to the positive electrode of the input voltage, and the other end is connected to the positive electrode of the input voltage. The second transistor and the second diode are connected to the supply voltage terminal; one end of the second resistor is connected to the positive pole of the input voltage, the other end is grounded through the first Zener diode, and the common terminal of the second resistor and the first Zener diode is connected to the second three The electrode is connected to the base electrode, and the first capacitor is connected between the power supply voltage terminal and the ground.

The output circuit is connected in series with a second NTC thermistor and an eighth diode.

The input undervoltage protection detection circuit includes a tenth resistor, an eleventh resistor, a twelfth resistor connected in series between the positive pole of the input voltage and the ground, and a sixth capacitor connected in parallel with the twelfth resistor, The common terminal of the eleventh resistor and the twelfth resistor is connected to the under-voltage protection function pin of the PWM drive control circuit.

The PWM drive control circuit adopts the NCP1252B type PWM control chip without intermittent and frequency reduction functions.

The constant current value adjustment circuit includes a third interface, and three terminals of the third interface are respectively connected with one end of the 28th resistor, the 29th resistor and the 30th resistor with different resistance values; the twentieth The other ends of the eighth resistor, the twenty-ninth resistor and the thirtieth resistor are grounded through the thirty-first resistor, and are connected to the constant current sampling feedback circuit at the same time; the thirty-first resistor is also connected with a sixteenth capacitor in parallel.

The input circuit is an anti-reverse input filter circuit, which includes a first NTC thermistor and a first diode connected in series on the circuit, and a first electrolytic capacitor connected in parallel on the circuit.

The overcurrent and overvoltage protection circuit includes a seventh resistor connected between the primary of the transformer of the power transmission output circuit and the ground, and the seventh resistor is connected to the primary of the transformer of the power transmission output circuit through the connection terminal. The eighth resistor is connected to the pin of the overvoltage protection function of the PWM drive control circuit; it also includes a second Zener diode, a third Zener diode and a third Zener diode connected in series between the output end of the power transmission output circuit and the eighth resistor. A voltage diode and a ninth resistor; a seventh capacitor is also connected between the common terminal of the eighth resistor and the ninth resistor and the ground.

The voltage-stabilizing sampling feedback circuit includes a twenty-first resistor and a twenty-second resistor for sampling the voltage at the output end of the power transmission output circuit, and a third interface for sampling the voltage at the output end of the power transmission output circuit. The provided quasi-reference voltage is compared, and a first comparator that provides a voltage stabilization feedback signal for the PWM drive control circuit.

A thirteenth resistor and an optocoupler device in series, and a fourteenth resistor and a fifth capacitor in parallel are arranged between the FB pin of the PWM control chip and the ground.

The beneficial effects of the present invention are as follows: the PWM control chip of the circuit of the present invention can be selected as a PWM control chip without functions such as intermittent, frequency reduction, etc., in the entire power terminal from light load to heavy load, the operating frequency will not change, and will not be intermittent, Frequency reduction; at the same time, the LDO power supply circuit is used to supply power to ensure a stable power supply to the PWM control chip, and for the problem of mis-triggering the overcurrent protection of the PWM control chip at startup, the overcurrent protection mode is changed from trigger mode to limit mode, and the output adopts The constant current value adjustment circuit is used to change the reference voltage mode to realize constant current in different gears, realize wide-range voltage regulation and constant current functions, and the NTC and diode are connected in series at the output end. When the output voltage is 0 V, the NTC and diode can be connected in series. Loss is generated to ensure that the PWM control chip works stably when the duty cycle is extremely small, and the constant current function when the output voltage is 0V can be realized. The circuit of the invention realizes the scheme of ultra-wide output voltage regulation and wide output constant current, and the current works stably, and has the functions of input undervoltage, input reverse connection, output overcurrent, overvoltage and short circuit protection.

Description of drawings

Fig. 1 is the circuit schematic diagram of the present invention;

FIG. 2 is a block diagram of the circuit principle of the present invention.

Detailed ways

The structure of the present invention will be further described below with reference to the accompanying drawings and preferred specific embodiments of the present invention.

Referring to FIG. 1 and FIG. 2, an ultra-wide output voltage and wide constant current range application circuit disclosed in the present invention includes: an input circuit, an LDO power supply circuit, a power transmission output circuit, an output circuit, and an input undervoltage protection Detection circuit, PWM drive control circuit, overcurrent and overvoltage protection circuit, voltage regulator sampling feedback circuit, constant current sampling feedback circuit and constant current value adjustment circuit.

The input circuit is used for DC power supply input, and supplies power to the LDO power supply circuit and the power transmission output circuit; the input circuit is preferably an anti-reverse input filter circuit. An NTC thermistor NTC1 and a first diode D1, and a first electrolytic capacitor EC1 connected in parallel on the circuit.

The LDO power supply circuit is used to convert the input voltage of the input circuit into a voltage required by a stable PWM drive control circuit to supply power to the PWM drive control circuit; in this embodiment, the LDO power supply circuit specifically includes a first resistor R1, the second resistor R2, the second transistor Q2, the second diode D2, the first Zener diode ZD1 and the first capacitor C1; one end of the first resistor R1 is connected to the positive electrode of the input voltage, and the other end is connected through the second triode The tube Q2 and the second diode D2 are connected to the power supply voltage terminal VCC, and the PWM drive control circuit and the voltage regulator sampling feedback circuit are powered through the power supply voltage terminal VCC; one end of the second resistor R2 is connected to the positive electrode of the input voltage, and the other end is regulated by the first voltage regulator The diode ZD1 is grounded, and the common terminal of the second resistor R2 and the first Zener diode ZD1 is connected to the base of the second transistor Q2. Under the constant voltage control of the first Zener diode ZD1 on the base of the second transistor Q2 , the power supply voltage terminal VCC maintains stable voltage output to the PWM drive control circuit and the voltage regulator sampling feedback circuit, and the first capacitor C1 is connected between the power supply voltage terminal VCC and the ground.

The power transmission output circuit is used to transform, rectify and filter the input voltage of the input circuit and then output it through the output circuit; in this embodiment, the MOS transistor Q1 of the power transmission output circuit is based on the drive pulse output by the PWM drive control circuit The signal performs the switching action, and the control transformer TID transfers the energy from the primary to the secondary. After the transformation is realized, it passes through the fifth diode D5, the third electrolytic capacitor EC3, the fourth electrolytic capacitor EC4, the first inductor L1, and the tenth After the rectification and filtering circuit formed by the six resistors R16 and the eighth capacitor C8 is rectified and filtered, it is outputted through the output circuit.

The output circuit is used for supplying power to the electrical equipment; in order to realize the anti-surge effect, the output circuit is connected to the output end by connecting the second NTC thermistor NTC2 and the eighth diode D8 in series.

The input under-voltage protection detection circuit is used to detect the input voltage of the input circuit, and when the input voltage is lower than the preset value, it provides an input under-voltage protection signal for the PWM drive control circuit, so as to prevent the input voltage from being too low and causing the invention to work unstable ; In this embodiment, the input undervoltage protection detection circuit specifically includes a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, and a The sixth capacitor C6 connected in parallel with the twelfth resistor R13, the common terminal of the eleventh resistor R11 and the twelfth resistor R12 is connected to the under-voltage protection function pin BO of the PWM drive control circuit; according to the tenth resistor R10, the eleventh resistor The resistance ratio of the resistor R11 and the twelfth resistor R12 determines the minimum input voltage value of the input circuit access voltage. When the input voltage is lower than the minimum input voltage value, the PWM drive control circuit enters the undervoltage protection state.

The overcurrent and overvoltage protection circuit is used to detect the output voltage of the power transmission output circuit and the primary current of the transformer of the power transmission output circuit. When setting the value, an overvoltage or overcurrent protection signal is provided for the PWM drive control circuit; in this embodiment, the overcurrent and overvoltage protection circuit specifically includes a voltage transformer connected between the primary of the power transmission output circuit and the ground. The seventh resistor R7 between the seventh resistor R7 and the primary connection end of the voltage transformer of the power transmission output circuit is connected to the overvoltage protection function pin CS of the PWM drive control circuit through the eighth resistor R8; it also includes The second Zener diode ZD2, the third Zener diode ZD3 and the ninth resistor R9 are connected in series between the output end Vo+ of the power transmission output circuit and the eighth resistor R8; the eighth resistor R8 and the ninth resistor R9 are in common A seventh capacitor C7 is also connected between the terminal and the ground, that is, the overcurrent and overvoltage protection circuit can monitor the primary input current and secondary output voltage of the transformer TID at the same time, whether it is the primary input current and secondary output voltage of the transformer TID. When the output voltage of each stage exceeds the preset range, it will trigger the PWM drive control circuit to enter the overvoltage protection state, that is, the overcurrent and overvoltage protection circuits realize output overvoltage detection and cycle-by-cycle current limiting, and provide feedback control for the PWM drive control circuit and protection.

The voltage regulator sampling feedback circuit is used to detect the output voltage of the power transmission output circuit, and compare it with the reference voltage provided by the constant current value adjustment circuit to provide the PWM duty cycle adjustment feedback signal for the PWM drive control circuit; in this embodiment, the voltage regulator The sampling feedback circuit includes a twenty-first resistor R21 and a twenty-second resistor R22 for sampling the input voltage of the output terminal Vo+ of the power transmission output circuit, and the sampling voltage obtained by sampling the output terminal Vo+ of the power transmission output circuit and the The quasi-reference voltage Vref provided by the third interface CON3 is compared, and the first comparator U2A that provides the voltage stabilization feedback signal for the PWM drive control circuit.

The constant current sampling feedback circuit is used to detect the output current of the power transmission output circuit and feed it back to the PWM drive control circuit; in this embodiment, the second comparator U2B, the seventeenth resistor R17 and the eighteenth resistor R18 , the ninth diode D9, the tenth diode D10, the ninth resistor R9, the seventh diode D7, the twenty-fifth resistor R25, the fourteenth capacitor 14, the twenty-sixth resistor R26, the thirteenth The peripheral circuit composed of the capacitor C13, the twenty-seventh resistor R27 and the fifteenth capacitor C15 is formed, and the constant current sampling feedback circuit adopts the existing circuit principle, which will not be described in detail here.

The constant current value adjustment circuit is used to adjust the reference value of the constant current sampling of the constant current sampling feedback circuit; in this embodiment, the constant current value adjustment circuit includes a third interface CON3, three of the third interface CON3 The terminals are respectively connected with one end of the twenty-eighth resistor R28, the twenty-ninth resistor R29 and the thirtieth resistor R30 with different resistance values; The other end is grounded through the thirty-first resistor R31, and is connected to the constant current sampling feedback circuit at the same time; the thirty-first resistor R31 is also connected in parallel with the sixteenth capacitor C16. In the specific application process, the constant current gear adjustment is realized through the third interface CON3.

The PWM drive control circuit is used to adjust the PWM duty cycle according to the feedback signals of the voltage regulation sampling feedback circuit and the constant current sampling feedback circuit, drive the power transmission output circuit, and perform undervoltage protection according to the input undervoltage protection signal of the input undervoltage protection detection circuit. Overvoltage protection, overcurrent protection is performed according to the overvoltage or overcurrent protection signal provided by the overcurrent and overvoltage protection circuit. In this embodiment, the PWM drive control circuit adopts the NCP1252B type PWM control chip U1 without intermittent and frequency reduction functions, and a thirteenth resistor R13 connected in series is set between the FB pin of the PWM control chip and the ground. and the optocoupler device OC1, as well as the fourteenth resistor R14 and the fifth capacitor C5 in parallel. The constant current sampling feedback circuit and the constant current value adjustment circuit provide the feedback signal for the PWM control chip U1 through the optocoupler device OC1 to adjust the duty ratio, so as to realize the output voltage regulation and constant current. In the circuit of the present invention, in order to realize the output ultra-wide voltage regulation range, the feedback speed of the constant current sampling feedback circuit and the constant current value adjustment circuit needs to be relatively slow. The charging process of the four electrolytic capacitors EC4 is relatively slow, and it is easy to accidentally trigger the overcurrent and overvoltage protection circuits to output overcurrent protection to pin 3 of the PWM control chip U1, and the fourteenth resistor R14 is used to clamp the 1st pin of the PWM control chip U1. The voltage on the pin, the voltage on pin 3 of the PWM control chip U1 will limit the duty cycle in advance before the overcurrent and overvoltage protection circuit triggers the overcurrent protection, which means that the overcurrent and overvoltage protection circuit cannot be triggered by mistake. The PWM control chip U1 enters the overcurrent protection state, but limits the maximum duty cycle, that is, limits the maximum output power. At the same time, when the output voltage of the present invention is switched between 0V-90V, or a wider voltage, the output The power will not be greatly increased suddenly, which improves the stability and reliability of the circuit.

The power transmission output circuit of the present invention adjusts the power delivered to the output terminal according to the duty ratio controlled by the PWM control chip U1, and outputs stable voltage and constant current after secondary rectification and filtering; the constant current value adjustment circuit can be used to change the reference way to output different constant current values, this method is better than changing the sampling current size; the output circuit is an output anti-surge circuit to prevent excessive surge current when the output switches between high and low voltages, and at the same time the first The addition of the second NTC thermistor NTC2 and the eighth diode D8 causes a voltage drop across the second NTC thermistor NTC2 and the eighth diode D8 when outputting 0V, which means that there is a minimum conversion power, Make sure that the PWM control chip U1 works stably at the minimum duty cycle, and the constant current can still be stable when outputting 0V. When the output circuit outputs 0V, the PWM control chip U1 is easy to run out of control, or it outputs too much current when it outputs 0V.

Claims (10)

1. An ultra-wide output voltage and wide constant current range application circuit is characterized by comprising: the device comprises an input circuit, an LDO power supply circuit, a power transmission output circuit, an input undervoltage protection detection circuit, a PWM (pulse-width modulation) drive control circuit, an overcurrent and overvoltage protection circuit, a voltage stabilization sampling feedback circuit, a constant current sampling feedback circuit and a constant current value regulating circuit; wherein,

the input circuit is used for direct current power supply input and supplying power to the LDO power supply circuit and the power transmission output circuit;

the LDO power supply circuit is used for converting the input voltage of the input circuit into the voltage required by the stable PWM driving control circuit and supplying power to the PWM driving control circuit;

the power transmission output circuit is used for carrying out voltage transformation, rectification and filtering on the input voltage of the input circuit and then outputting the input voltage through the output circuit;

the output circuit is used for supplying power to the electric equipment;

the input undervoltage protection detection circuit is used for detecting the input voltage of the input circuit and providing an input undervoltage protection signal for the PWM drive control circuit when the input voltage is lower than a preset value;

the over-current and over-voltage protection circuit is used for detecting the output voltage of the power transmission output circuit and the primary current of the transformer of the power transmission output circuit, and providing an over-voltage or over-current protection signal for the PWM drive control circuit when the output voltage of the power transmission output circuit is detected to be higher than a preset value or when the primary current of the transformer is larger than the preset value;

the voltage-stabilizing sampling feedback circuit is used for detecting the output voltage of the power transmission output circuit, comparing the output voltage with the reference voltage provided by the constant current value regulating circuit and providing a PWM duty ratio regulating feedback signal for the PWM driving control circuit;

the constant-current sampling feedback circuit is used for detecting the output current of the power transmission output circuit and feeding back the output current to the PWM driving control circuit;

the constant current value regulating circuit is used for regulating a constant current sampling reference value of the constant current sampling feedback circuit;

and the PWM driving control circuit is used for adjusting the PWM duty ratio according to feedback signals of the voltage-stabilizing sampling feedback circuit and the constant-current sampling feedback circuit, driving the power transmission output circuit, performing undervoltage protection according to an input undervoltage protection signal of the input undervoltage protection detection circuit, and performing overcurrent protection according to an overvoltage or overcurrent protection signal provided by the overcurrent and overvoltage protection circuit.

2. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the LDO power supply circuit comprises a first resistor, a second triode, a second diode, a first voltage stabilizing diode and a first capacitor; one end of the first resistor is connected with the positive electrode of the input voltage, and the other end of the first resistor is connected with a power supply voltage end through the second triode and the second diode; one end of the second resistor is connected with the positive electrode of the input voltage, the other end of the second resistor is grounded through the first voltage stabilizing diode, the common end of the second resistor and the first voltage stabilizing diode is connected with the base electrode of the second triode, and the first capacitor is connected between the power supply voltage end and the ground.

3. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the output circuit is connected in series with a second NTC thermistor and an eighth diode.

4. A superwide output voltage and wide constant current range application circuit, as claimed in claim 1, wherein: the input undervoltage protection detection circuit comprises a tenth resistor, an eleventh resistor, a twelfth resistor and a sixth capacitor, wherein the tenth resistor, the eleventh resistor and the twelfth resistor are sequentially arranged between the positive electrode of the input voltage and the ground in series, the sixth capacitor is connected with the twelfth resistor in parallel, and the eleventh resistor is connected with an undervoltage protection function pin of a PWM (pulse width modulation) drive control circuit connected with the common end of the twelfth resistor.

5. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the PWM driving control circuit adopts an NCP1252B PWM control chip without intermittence and frequency reduction functions.

6. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the constant current value regulating circuit comprises a third interface, and three terminals of the third interface are respectively connected with one ends of a twenty-eighth resistor, a twenty-ninth resistor and a thirty-eighth resistor which are different in resistance value; the other ends of the twenty-eighth resistor, the twenty-ninth resistor and the thirty-eighth resistor are grounded through a thirty-first resistor and are simultaneously connected with a constant current sampling feedback circuit; and the sixteenth capacitor is connected in parallel with the thirty-first resistor.

7. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the input circuit is an anti-reverse connection input filter circuit and comprises a first NTC thermistor and a first diode which are connected in series on the circuit, and a first electrolytic capacitor which is connected in parallel on the circuit.

8. A superwide output voltage and wide constant current range application circuit according to claim 1, wherein: the overcurrent and overvoltage protection circuit comprises a seventh resistor connected between the primary side of a transformer of the power transmission output circuit and the ground, and the connecting end of the seventh resistor and the primary side of the transformer of the power transmission output circuit is connected with the overvoltage protection function pin of the PWM drive control circuit through an eighth resistor; the power transmission output circuit also comprises a second voltage-stabilizing diode, a third voltage-stabilizing diode and a ninth resistor which are connected in series between the output end of the power transmission output circuit and the eighth resistor; and a seventh capacitor is connected between the common end of the eighth resistor and the ninth resistor and the ground.

9. A superwide output voltage and wide constant current range application circuit according to claim 6, wherein: the voltage-stabilizing sampling feedback circuit comprises a twenty-first resistor and a twenty-second resistor which are used for sampling the voltage at the output end of the power transmission output circuit, and a first comparator which is used for comparing the sampling voltage at the output end of the power transmission output circuit with the reference voltage provided by the third interface and providing a voltage-stabilizing feedback signal for the PWM driving control circuit.

10. A superwide output voltage and wide constant current range application circuit according to claim 5, wherein: and a thirteenth resistor and an optocoupler device which are connected in series, a fourteenth resistor and a fifth capacitor which are connected in parallel are arranged between the FB pin of the PWM control chip and the ground.

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